Harry Potter. Not only have these wonderful buku inspired me creatively (I don't even know how many HP themed school projects I've done; the latest was for my college Psychology class), but they've been an enormous sumber of comfort and inspiration in my personal life. They made me decide not to commit suicide. That's pretty inspirational.
Basically what I'm saying is, the Harry Potter series is the Luna to my Harry.
I think... the School for Good and Evil oleh Soman Chainani. It's a great book, and all should read it. It's not just for kids, too, it's kind of a YA book, because people die and there are slight romantic themes.